The present invention relates to a method of operating an arc welding apparatus by detecting and releasing the weld of a work with a welding wire (simply referred to as a wire hereinafter).
According to such a method of the operating arc welding apparatus, after completion of an arc welding process, a determine is made to whether or not the wire is surely bonded to the work. As one method of determining if the work is properly banded to the wire, a DC voltage is applied to the wire and then the change of the voltage is detected. More specifically, a DC voltage is applied to the wire while the work is grounded. If the work and the wire are properly welded to each other, the wire is grounded via the work, consequently decreasing the voltage approximately to zero.
The relationship between the wire and the work during at the above noted detecting time-is shown in FIGS. 8-10. FIG. 8 indicates the state where a wire 9 set at the front end of a torch 5 is completely separated away from a work 8. FIG. 9 shows the wire 9 slipping down and thus barely touching the work 8 when the welding process has been completed (described as a pseudo welding state hereinafter). Meanwhile, the wire 9 is welded to the work 8 in FIG. 10. The torch 5 is moved to a next welding process only in the state shown in FIG. 8 where the wire 9 is perfectly detached from the work 8, and in the other cases, a welding voltage is impressed to fuse the wire 9 or the welding system is halted and the welded state of the wire 9 is displayed. A fusing process for the wire 9 is needed only in FIG. 10, that is, the torch 5 can be moved to a next welding process except for the case of FIG. 10 where the wire 9 is perfectly welded to the work 8. In other words, although the torch 5 can be sent to a next process promptly subsequent to the state of the pseudo welding in FIG. 9, the fusing process has been actually carried out in the prior art.
In order to remove such inconveniences, there have been provided a welding method disclosed in, for instance, Japanese Patent Publication No. 62-54586 (54586/1987) wherein a torch is always moved a predetermined distance corresponding to the play of a wire in a direction away from a work so as to inspect the welded state between the wire and the work.
However, the method has the following inconveniences.
(1) Even when the welding is finished in the state as shown in FIG. 8, the torch 5 has to be moved after the welding process so as to inspect the welded state between the wire and the work although it is unnecessary. Therefore, the time for the welding process cannot be shortened. PA1 (2) It is necessary to control the torch 5 to move in a direction which does not interfere with a tool or the work 8 after welding. Moreover, it is necessary for the torch 5 to separate the wire 9 in a direction away from the work 8 for each terminal point of welding. To control the torch 5 as above hinders shortening of the time for the welding process. PA1 (3) In the case shown in FIG. 10 where the wire 9 is welded to the work 8, the wire 9 is kept clamped by a wire feeding device and therefore, the torch 5 interferes with the wire 9 if the torch 5 is moved in a direction not coincident with the feeding direction of the wire 9, thereby breaking a torch holding part. PA1 (4) A mechanism for releasing the torch 5 after welding is needed (the prior art requires a robot for this purpose).